1. Field of Use
This invention relates to fabricating containment vessels such as rocket motor cases that have an internal lining comprising elastomer. This invention, more specifically, relates to a method of fabricating these elastomer lined vessels where a tacky ribbon comprising cured or curable elastomer is used in providing the liner on the inside of a previously made composite or metal structural shell of the containment vessel.
2. Prior Art
The elastomeric liner of containment vessels performs such functions as a sealant to (a) retain the fluid contents, (b) prevent contamination of the contents from external sources, and (c) protect the composite or metal structural body from chemical or thermal degradation. For example, where the vessel is a rocket motor case, either composite or metal, the elastomeric liner serves the major function of thermally insulating the case from the hot combustion gases of the burning rocket fuel. For rocket motor cases, two present methods of insulator manufacture are (1) the molding of green rubber stock in matched metal dies and (2) the hand lay-up of green rubber sheets followed by vulcanization and grinding to final dimensions. In either circumstance, insulators for composite cases are next positioned on case winding mandrels, or for a preformed case, formed within it, where various splicing, hand buffing, bonding and shrinking operations are performed.
For very large rocket motors using either metal or composite as the structural body and in which the insulator is positioned within the preformed case, special care must be exercised prior to vulcanizing to prevent the elastomer from debonding from the "ceiling"]side of the case, falling to the "floor" with loss of significant monies, and possibly causing major injury or death.
For small rocket motor cases (typically 5 cm to 50 cm diameter) one method of insulator manufacture is the hand lay-up of green rubber sheets on a metal mandrel with an expandable cured elastomeric skin. The mandrel is inserted into the case, then the elastomeric skin is expanded to force the green rubber insulator into contact with the case wall where it is retained during vulcanization.
These methods of fabrication are disadvantageous in view of the need for: a) large facility investments, b) extensive precision tooling, c) long lead times for production that give rise to an inability to accommodate design changes quickly and cheaply, and d) labor intensive unit costs.
U.S. Pat. No. 3,303,079 relates to preparation of elastomer lined rocket motor cases. This patent proposes laying calendared sheets of rubber on a mandrel to produce an elastomer precursor layer to the liner. The elastomer layer is encased in a resin and filament wound shell and the resin and elastomer cured together in providing the elastomer lined composite vessel. Laying calendared sheets manually about a mandrel, however, is labor intensive; and it is especially difficult when building thickness with more than two sheets of the elastomer and when covering contoured portions of the mandrel with precise, but variable thicknesses.
This application is a continuation in part of U.S. patent application Ser. No. 378,588, filed May 17, 1982, now U.S. Pat. No. 4,596,619.